On its first day fifty states from across the world signed the treaty. The TPNW makes nuclear weapons illegal for its states parties, and also obliges them to assist the victims of nuclear weapons use and testing and take steps to remediate environments affected by these horrific weapons of mass destruction. Thailand, the Holy See and Guyana also ratified the treaty today. It will enter in to force when fifty states have ratified it.

The President of Chile, Michelle Bachelet, signs the Treaty on the Prohibition of Nuclear Weapons at the UN in New York (Darren Ornitz/ICAN)

Before the negotiation of the TPNW, nuclear weapons were the only weapons of mass destruction not prohibited by an international treaty.

An examination of the evidence of the catastrophic and insurmountable humanitarian consequences of nuclear weapons, by states, international organisations and civil society, led the majority of the world’s states to conclude that a treaty on their prohibition had to be agreed – with or without the initial participation of the nuclear armed states. The treaty nevertheless provides a framework for states with stockpiles of nuclear weapons, and those that host nuclear weapons on their territory, to join the treaty and get rid of these weapons, as other disarmament treaties do.

As Beatrice Fihn, Executive Director of the International Campaign to Abolish Nuclear Weapons (ICAN) said in her remarks on behalf of civil society to today’s ceremony: “Important progress is rarely easy…progress doesn’t just happen when everyone is ready, it must be fought for.” She added: “you are the states that are showing moral leadership – in a world that desperately needs moral leadership today.”

The signing ceremony opened with reflections from UN Secretary-General Antonion Guterres, the President of the General Assembly, Miroslav Lajčák of Slovakia, the President of Costa Rica, Luis Guillermo Solís, the President of the International Committee of the Red Cross, Peter Maurer, and Fihn.

The Treaty on the Prohibition of Nuclear Weapons (UN Photo/Kim Haughton)

All placed a heavy emphasis in their remarks on the devastating impacts of nuclear weapons, which have led to the negotiation of this treaty, and on the suffering of those affected by nuclear weapons use and testing, which must never be allowed to happen again. The contribution of the survivors of nuclear weapons testing and the atomic bombings of Japan to the process to bring about the treaty was noted by the speakers, who highlighted their suffering, struggle and courage and their testimony on the unacceptable impact of nuclear weapons. The key role of civil society in bringing the treaty about was also emphasised by speakers.

Guterres welcomed the treaty as an historic milestone towards the elimination of nuclear weapons, which pose grave risks to our world, declaring “we cannot allow these doomsday weapons to endanger our world and our children’s future.”

Lajčák emphasised the devastating impacts of nuclear weapons in both scale and longevity, and welcomed the treaty’s contribution towards achieving a world free of nuclear weapons, noting the initiative it showed from states and the importance it would have to raising awareness.

Guillermo Solís declared Costa Rica’s unwavering commitment that there should be no further victims of nuclear weapons – as no person should experience the suffering that hibakusha had been through – and emphasised to the states present that their signature of the treaty was on behalf of all those who had suffered from the atomic bombings of Japan and the testing of nuclear weapons. He thanked states for their efforts on behalf of future generations, stating with pride that we can now say to our children that nuclear weapons are prohibited around the world. Guillermo Solís regretted that those countries still claiming a benefit from nuclear weapons were for now remaining outside the course of history through not joining this global initiative of the human family.

The Red Cross movement played a key role in bringing the treaty about. Maurer declared the TPNW “a light for all humanity”. He recalled the “chilling” cable received from Red Cross doctors in Hiroshima describing the scale of the catastrophe – a message that they never want to receive again. Maurer noted that the more powerful weapons in arsenals today would have even more devastating impacts – and that the humanitarian response capacity would not be adequate. He emphasised the treaty’s importance to delegitimising the role of nuclear weapons in the world today, prohibiting them on the basis of international law. Maurer described signing the treaty as a humanitarian imperative, and urged states to work towards its implementation.

Fihn noted that ICAN had worked long and hard for this treaty, and that its agreement represented international law standing up against weapons of mass destruction. She noted that the treaty has been called “divisive” by those who still value nuclear weapons, who are opposed to this initiative, but that the TPNW is based on strong foundations, being morally right and coherent with the framework of international law.

As she noted, weapons that cause unacceptable harm to civilians cannot remain legal. In prohibiting nuclear weapons, the TPNW takes a major step forward for this principle and for humanity.